Preterm labour induction: modalities, implications and outcomes

Objective: To evaluate the association between induction method and caesarean delivery rate, as well as perinatal outcomes, among women undergoing preterm labour induction. Methods: This retrospective cohort study was conducted at a university-affiliated medical centre between 2011 and 2024. Women with singleton pregnancies undergoing labour induction between 29 + 0 and 36 + 6 weeks of gestation were included. Induction methods included prostaglandins, balloon catheter followed by oxytocin, and oxytocin alone. Multi-variable logistic regression was used to assess associations between induction method and caesarean delivery, adjusting for maternal age, parity, birth weight, birthweight percentile, diabetes and pre-eclampsia. Subgroup analyses evaluated risk of caesarean delivery by gestational age (<34, 34, 35 and 36 weeks), birthweight percentile and presence of pre-eclampsia. Results: Among 563 preterm inductions, 289 were performed with prostaglandins, 102 with a balloon catheter followed by oxytocin, and 172 with oxytocin alone. The caesarean delivery rates were 10.7 %, 30.4 % and 21.5 %, respectively (p < 0.001). Prostaglandins were associated with the lowest odds of caesarean delivery. In comparison, the balloon catheter followed by oxytocin [odds ratio (OR) 3.12, 95 % confidence interval (CI) 1.65–5.88] and oxytocin alone (OR 2.14, 95 % CI 1.23–3.70) were associated with higher odds of caesarean delivery. No significant difference was found between the odds of caesarean delivery for balloon catheter followed by oxytocin, and oxytocin alone (OR 0.69, 95 % CI 0.37–1.28). Higher maternal age, lower birthweight percentile, and the presence of pre-eclampsia were independently associated with increased risk of caesarean delivery. Prostaglandins were associated with the lowest caesarean delivery rates among non-small-for-gestational-age neonates and women without pre-eclampsia. No significant differences were observed in adverse neonatal outcomes, including umbilical pH ≤ 7.0, fetal or neonatal death, or uterine rupture. Conclusion: In moderate-to-late preterm gestations, prostaglandins were associated with lower caesarean delivery rates compared with oxytocin alone and balloon catheter followed by oxytocin, with no differences in adverse neonatal outcomes. These findings support the relative safety and feasibility of prostaglandins for preterm induction.